Electric discharge device utilizing novel sealing means



March 19, 1963 A. w. COOLIDGE, JR 3,082,347

ELECTRIC DISCHARGE DEVICE UTILIZING NOVEL SEALING MEANS Filed Dec. 11, 1959 FIG.|.

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' INVENTOR:

f" ARTHUR W.COOLIDGE,JR. 19 2 I I 25 W w I7 18 8 HIS ATTORNEY.

United States Patent 3,082,347 ELECTRIC DISCHARGE DEVICE UTILIZING NOVEL SEALING MEANS Arthur William Coolidge, Jr., Scotia, N.Y., assignor to General Electric Company, a corporation of New York Filed Dec. 11, 1959, Ser. No. 858,956 9 Claims. (Cl. 313-250) My invention relates to electric discharge devices and pertains more particularly to improved envelope structures therefor.

Heretofore, electric discharge devices have been manufactured with ceramic-and-metal envelopes completed by first stacking the various ceramic and metal elements in a desired manner and then placing the stacked assembly in a brazing furnace, thereby to bond the several elements to complete the envelope. Following such an operation the complete envelope is usually tested to detect leaks and when a leak is encountered it is generally necessary to discard or reconstruct the whole assembly. Further, in manufacturing a device in this manner the size of the available brazing furnace is a decided limitation on the size of the envelope to 'be constructed. Still further, in ceramic and metal tube envelope constructions the metal sealing rings generally serve as electrical contacts for electrodes contained in the envelope which require the making of some electrical connections between the sealing. rings and electrode-supporting members in the envelope. In prior art devices expansion and contractions of the electrode-supporting members have resulted in seal failures.

Additionally, in some prior art ccramic-and-metal envelope assemblies difliculties have been encountered in incorporating in the structures cooling arrangements which will not subtract from the effectiveness and strength of ceramic-to-metal seals in the structure. Also, difliculties have been encountered in the appearance of corona at the seals which have caused undesirable effects, such as damage to the insulation of equipment parts adjacent the tube.

My invention contemplates the provision of an envelope construction adapted for being fabricated in individual ceramic-and-metal sub-assemblies or modules which can be individually tested for leaks and subsequently joined using any number of desired modules to complete an envelope construction of any desired size. Additionally, my invention contemplates the provision of sealing arrangements whereby the subsequent assembly may be readily disassembled, reworked and rescaled should this be necessary, as well as the provision of means for effecting a satisfactory electrical connection between electrode-supporting members in the envelope and the sealing rings, while minimizing undesirable transmission of strain to the sealing rings. Further, my invention contemplates the provision of a fluid-cooled anode arrangement wherein the cooling means is supported rigidly and for minimizing stresses at the adjacent seals. Still further, my invention contemplates provision of means for avoiding corona formation in those regions of the device where corona is prone to appear.

Accordingly, the primary object of my invention is to provide a new and improved ceramic-and-metal envelope construction.

Another object of my invention is to provide a new and improved ceramic-and-metal envelope construction, the

size of which is not limited by the size of available brazing furnaces.

Another object of my invention is to provide new and improved means for enabling the testing for faulty seals between ceramic and metal components of an envelope construction before completion of the assembly of the over-all envelope.

3,082,347 Patented Mar. 19, 1 963 Another object of my invention is to provide a new and improved sealing arrangement which enables and facilitates the reworking of a defective envelope assembly and the reuse of component parts.

Another object of my invention is to provide a new and improved ceramic-andmetal electric discharge device envelope including improved anode sealing means.

Another object of my invention is to provide an improved ceramic-and-metal envelope structure for an electric discharge device incorporating improved means for minimizing undesirable corona formations.

Still another object of my invention is to provide a new and improved combined envelope seal and electrical contact arrangement which minimizes transmission to the seals of any strain from electrode-supporting members contained in the envelope. Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming part of this specification.

In carrying out the objects of my invention I provide an electric discharge device including a ceramic-and-metal envelope containing at least a partially reduced atmosphere and comprising a plurality of ceramic wall sections each having bonded thereto a sealing ring. The sealing ring provides a lap seal between it and the outer surface of the wall section and includes a flat radial flange extending a substantial distance outwardly of the ceramic section. A pair of ceramic wall sections are joined by a bead weld between the edges of the outwardly extending flanges of sealing rings on adjacent opposed ends of the wall sections. The cathode end of the envelope is closed by a similar weld between the edge of the flange of a sealing ring on the outer end of a ceramic wall section and a similar flange on a metal end member of the envelope. Electrode support members in the envelope include outwardly extending flanges disposed between but not directly connected mechanically to the sealing rings. Spacers corresponding in thickness generally to the thickness of the supporting-member flange are welded in place between the outwardly extending flanges of the sealing rings. A plurality of electrode-supporting member flanges can be positioned between the sealing rings, in which case a spacer or plurality of spacers equal in total thickness generally to the combined thickness of the support member flanges is positioned and welded between the outer flanges of the sealing rings. The anode end of the envelope is closed by a cup-like anode member reentrant in the uppermost ceramic wall section and includes a flat flange sealed to a flat annulus which, in turn, is sealed at the outer edge thereof by a bead weld to the outer rim of one of the described sealing rings bonded to the upper end of the uppermost ceramic section. Bonded to the bottom of the anode member is a cooling fluid conduit including upwardly extending end portions. The end portions are bonded in a flat annulus joined at the rim thereof'to the first-mentioned annulus by the same bead weld which joins the latter to the sealing ring. Provided about at least one of the sealing rings and covering the U-shaped section thereof and extending into the region between that section and the outer wall of the corresponding ceramic section is an annulus of a high heat resistant insulative material.

For a better understanding of my invention, reference may be had to the accompanying drawing wherein:

FiGURE 1 is a sectionalized partially fragmentary illustration of an electric discharge device constructed in accordance with the several features of my invention;

*FIGURE 2 is an enlarged fragmentary sectional view grid-supporting member.

of a seal between ceramic sections according to my invention;

FIGURE 3 is an enlarged fragmentary sectional view of the envelope end sealing arrangement of my invention; and

:FIGURE 4 is an enlarged fragmentary sectional view illustrating a modified form of my sealing arrangement.

Referring to FIGURE 1, the various features of my invention are therein illustrated in an electric discharge device of the hydrogen thyratron type comprising an envelope 1, a cathode and reservoir assembly 2, a first grid assembly 3, second grid assembly 4, and an anode assembly 5.

The envelope 1 comprises three generally tubular axially aligned ceramic insulator sections 6, 7 and 8. The sections 68 may be formed of any suitable high-strength and highly refractory ceramic material adapted for being metalized in order to facilitate the provision of ceramicto-metal bonds between the insulator sections and metallic sealing rings disposed therebetween. For example, the sections 6 to 8 may be suitably formed of ceramic materials generally known in the art as alumina, which materials are adapted for being provided with metalized areas in the manner disclosed in US. Patent 2,667,427 issued January 26, 1954 to Henry J. Nolte and assigned to the same assignee as the present invention.

The cathode and reservoir assembly 2 includes a header 10 closing the lower end of the envelope 1. The header 10 supports in, a suitably insulated manner a plurality of electrical leads 11 which extends through the header in a sealed manner and internally of the envelope support and make suitable electrical connections to a cathode structure 12 and a hydrogen reservoir 13. Electrically connected to the outer ends of the leads 11 are flexible conductors 14. The header 10 is suitably hermetically bonded, as by a bead weld, in a tubular sealing ring 15 formed to include a flat flange 16 extending radially outwardly of the envelope wall a substantial distance. Sealed to the flange 16 is a sealing ring generally designate-d 17 which can be suitably formed of copper- .clad chrome iron. The sealing ring 17 is shaped to include a U-shaped section 18, a flat flange 19 extending outwardly a substantial distance from the U-shaped section and a relatively short flat inwardly extending flange 20. The edges of the flanges 16 and 19 are in register and are hermetically bonded by a bead weld 21.

The lower end of the ceramic section 6 is disposed in the sealing ring 17 and the'inner side portion of the U- shaped section 18 of the ring is bonded to a suitably previously metalized lower end of the ceramic insulator 6, as my means of a silver-copper brazing material. Thus a lap seal is provided between the side surface of the lower end of the ceramic 6 and the sealing ring and a highly satisfactory compression seal is thereby provided between the sealing ring 17 and the lower end of the ceramic.

Extending into the ceramic 7 is a cup-like grid supporting element including an outwardly extending flange 22 positioned between the flanges 20 of the sealing members on the opposed ends of ceramics 6 and 7. In the illustrated structure a single flanged cup-like element having a perforate bottom comprises both the grid and the However, if desired, the element actually comprising the grid can be supported a separate tubular flanged support member. The flange 22 is positioned between the flanges 20 of a pair of sealing rings 17 bonded to the opposed ends of the ceramic sections 6 and 7 in the same manner as the previously described ceramic 17 is brazed to the lower end of the ceramic 6. This structure is perhaps better seen in FIG- sure of the envelope.

thickness generally to the thickness of the flange 22 of the grid support member and has an inner diameter at least slightly greater than the outer diameter of the grid support flange 22 so as to avoid stress-transmitting engagement. The outer edge of .the spacer 23 and the outer edges of the flanges 19 are in register and are joined by a bead weld 24. The grid cup 3 can be supported and sealed in the envelope between the ceramic sections 7 and 8 in the same manner as the grid 4.

Sealed to the upper end of the ceramic section 8 is another sealing ring 17 brazed to the upper end of the section 8 in the same manner as the previously described rings 17 are brazed to the other ends of the ceramic sections 68. Extending into the ceramic section 8 is a cup-like anode member which also serves as the end c1o- As perhaps better seen in FIG- URE 3, the cup-like member 25 includes an outwardly extending flange 26 which rests upon the inwardly extending flange 20 of the sealing ring 17 and is bonded at its edge in a step 27 formed in a relatively thicker circular flat annulus or sealing plate 28. The sealing plate 28 corresponds in outer diameter to the flange 19 of the sealing ring 17 and the outer edges of these elements are in register and hermetically joined by a bead weld 29.

Provided for assisting in the cooling of the anode is a cooling fiuid conduit 30. The conduit 30 includes a flat coiled portion 31 and a pair of upright end portions 32. The coil portion is bonded in a high heat transferring manner to a thermally conductive plate 33 which is, in turn, similarly bonded to the bottom of the cup-like anode member. Thus, a cooling fluid circulated through the conduit is effective for carrying away heat from the anode. Mounted centrally in the plate 33 is an anode terminal post 34.

Provided for supporting the upright end portions 32 of the conduit is a metal annulus 35. The annulus 35 is provided with suitable apertures through which the ends of the portions 32 of the conduit extend for being secured in a suitable manner to the annulus. If desired the ends of the portions 32 can be provided with connectors for connecting the conduit in a fluid circulating system. The annulus 35 is bonded at the outer edge thereof to both the annulus 28 and the sealing ring flange 19 by the bead weld 29. Additionally, the central opening of the annulus provides access to the'terminal post 34, and the rim of the opening is turned down to lend greater rigidity to the annulus.

It will be understood from the foregoing that the arrangement including the annulus bonded to the members 29 and 19 provides for sturdy mounting of the conduit ends on the upper end of the tube without adversely affecting the ceramic-and-metal seal thereof, the annulus 28 and the sealing ring 17 being efiective for minimizing the transmission of stresses from the coil supporting annulus 35 to the uppermost ceramic-to-metal seal.

Additionally, .I have found that the close relative positioning of the anode cup wall and the upper end portion of the grid cup 3 has resulted in a tendency for corona to form in the exterior of the insulator section 8 in the region generally designated 36 and located between the insulator 8 and the U-shaped portion of the upper sealmg ring 17. In order to prevent such formation and thus minimize possible damage to apparatus that may be. located adjacent the tube I have provided an annulus of a high heat-resistant material such, for example, as silicone rubber which extends downwardly in the region 36 and embeds the U-shaped section of the sealing ring while leaving the flange 19 exposed for welding during assembly and cutting if it should become necessary to disassemble the tube for reworking.

It will be understood from the foregoing that the described scaling arrangements enable sub-assemblies or modules including, for example, a ceramic section and a pair of sealing rings 17 to be assembled independently and tested for leaks of the seals therebetween. Additionally, the anode sub-assembly including the described cooling means can be separately constructed, as can the sub-assembly including the corona inhibiting structure. Should a leak be detected in any one of these sub-assemblies, it can either be repaired or discarded. Subsequently, a number of sub-assemblies can be easily assembled by stacking in the manner shown with the grid cups set in place between appropriate sub-assemblies and by joining by means of the bead welds the adjacent flanges such, for example, as the flanges 16 and 19 at the lower end of the assembly or the flanges 19 in the intermediate portions of the assembly or the flanges 19 and 28 at the upper end of the assembly. By so uniting the flanges the device can be hermetically sealed without inserting the over-all device in a brazing furnace. Additionally, should a leak be detected in the thus assembled structure any one of the bead welds joining the flanges can be easily cut away and subsequently rewelded after correction of the defect or insertion of a non-defective sub-assembly.

Still further, when the device is at least partially evacuated the axial thrust on the ends of the assembly afforded by external atmospheric pressure serves to press the envelope elements together, whereby the flanges 22 of the grid elements are securely held in place. Thus, these elements are assured of being held in place in satisfactory electrical contract between the sealing rings without the transfer to the seals of any undesired strains resulting from thermal expansion and contraction of the grid cups which could result were the flanges 22 bonded to any portion of the sealing rings 17. Additionally, in my arrangement it is possible to lift these parts out of the assembly easily should it become necessary to separate the sub-assemblies and rework the parts. The spacers 23 at the grid contact seals serve to avoid any undesirable stresses in the sealing ring 17 which might occur where it is necessary to compress the flanges together to compensate for the spacing between the inner flanges 20 weld 43 is alsd connected with a pair of spacers 44 which together total the combined thickness of the flanges 41 on the cups 40. Alternatively, a single spacer can be employed, provided its thickness generally equals the combined thicknesses of the flanges 41. In this embodiment also the inner diameter of the spacers 44 is greater than the outer diameter of the flanges 41 to avoid any direct contact between these elements which could result in strains being transmitted to the seals between the sealing rings 17 and the ceramic sections. It will be understood, however, that if the flanges 41 should expand sufficiently and engage the spacers 44 the latter elements will have some desirable constraining effect as does the annulus at the upper end of the envelope.

While I have described specific embodiments of my invention 1 do not desire my invention to be limited to the particular forms known and described that I intend by the appended claims to cover all modification within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

,1. An electric discharge device envelope comprisinga' tubular ceramic wall section, a metal sealing ring including an integral generally U-shaped section and a flat flange extending radially a substantial distance outwardly of said U-shaped section, said wall section being disposed in said sealing ring and having the outer side surface thereof lap-sealed to the inner side portion of said U- shaped section by a metallic bond to provide a hermetic compression seal therebetween, another Wall section of said envelope bearing on said first-mentioned wall seccaused by'the insertion therebetween of the flanges 22. 1

However, it will be understood that in some applications the flanges 19 can be sufliciently thin and Wide radially so that they can be easily pressed together for welding without enlarging the seals and thus avoiding the need for the mentioned spacers. The use of the spacers 23 also avoids the necessity for forming the flanges 19 and 20 of the sealing rings at different axial levels. the sealing rings 17 can he of uniform simple manufacture and spacers of diflerent thicknesses can be employed where necessary.

Additionally, the flange 26 of the anode cup is not bonded to the flange 20 of the uppermost sealing ring 17 and, thus, any expansion or contraction movement of the flange 26 is not transmitted directly to the ceramicto-metal seals at the upper end of the device. In this arrangement the heavier ring 28 serves to constrain such thermal expansion and contraction movements of the flange 26 as does the annulus 35. Additionally, any strain that would ordinarily be transmitted to the sealing ring 17 through the plate 28 will be absorbed by the U-shaped section of the sealing ring.

Still further, the U-shaped section of the rings 17 provide for the lap seal between the rings and the ceramic insulators.

In some structures it is desirable to define within a device a hollow metal assembly such as a cavitygrid. As illustrated in FIGURE 4, my invention enables the construction of such an assembly employing a pair of opposed cup-like grid elements 40 including outwardly extending flanges 41 in abutting relation and disposed between the flanges 20 of a pair of sealing members 17 of the type described above and sealed to the ends of a pair of ceramic sections 42 which can be identical to the above-described ceramic sections. In this arrangement the flanges 19 of the sealing rings 17 are joined at their registering outer edges by a bead weld 43. The head Thus,

tion and including a flat radially outwardly extending metal flangehaving an edge registering with that of said first-mentioned flange, and a metallic bond joining only the registering edges of said flanges.

2. An electric discharge device comprising an envelope containing a reduced atmosphere and including a tubular ceramic wall section, a metal sealing ring including an integral generally U-shaped section and a flat flange extending radially a substantial distance outwardly from said U-shaped section, said wall section being disposed in said sealing ring and having the outer side surface thereof lap-sealed to the inner side portion of said U- shaped section by a metallic bond, another wall section bearing on the end of said first-mentioned wall section and including a radially outwardly extending flat metal flange having an edge registering with that of said firstmentioned flange, a metallic bond uniting the registering edges of said flanges, and cup-shaped electrode extending reentrantly in one of said Wall sections and including a flat radial flange positioned between the first and secondmentioned flanges and not fixed to any of the aforesaid elements, whereby the axial atmospheric thrust on both ends of said envelope is effective for holding said electrode in place and the transmission of strain from sald electrode to said metallic bonds is minimized.

3. An electric discharge device according to claim 2, wherein at least one circular spacer corresponding generally in thickness to the thickness of said electrode flange is interposed between the outer edges of said first and second-mentioned flanges, and said metallic bond at the outer edges of said flanges unites the registering edges of said first and second-mentioned flanges and said spacer.

4. An electric discharge device comprising a pair of axially aligned tubular ceramic wall sections, a pair of sealing rings each including an integral U-shaped section, a flat flange extending radially a substantial distance outwardly of the U-shaped section and a relatively short flange extending inwardly of said U-shaped section, said pair of sealing rings having the U-shaped sections thereof oppositely disposed, having the edges of said outwardly extending flanges registering and united by a metallic bond and having the relatively short flanges thereof in mutual bearing relation, and said wall sections each hav- 7 ing an end disposed in one of said sealing rings and having the outer surface thereof lap-sealed to the inner side portion of the U-shaped section thereof to provide a compression seal therebetween and the end surface bearing on said inwardly extending flange.

5. An electric discharge device according to claim 4-, wherein a supporting member extends in one said ceramic sections and includes an outwardly extending flange positioned between said inwardly extending flanges of said seal-ing rings, and a circular spacer corresponding in thickness generally to said supporting member flange and having an infi'er diameter greater than the outer diameter of said last-mentioned flange and is sealed between said outwardly extending flanges of said sealing rings.

6. An'electric discharge device according to claim 4, wherein a pair of oppositely disposed cup-shaped electrode members each extends reentrantly in one of said ceramic sections and include outwardly extending abutting flanges which are positioned between said inwardly extending flanges of said sealing rings but are directly unconnected thereto, and at least one circular spacer corresponding in thickness generally to the thickness of said supporting member flanges and having an inner diameter greater than the outer diameter of said last-mentioned flange is sealed between said outwardly extending flanges of said sealing rings.

7. An electric discharge device comprising a tubular ceramic wall section, a sealing ring including an integral U-shaped section, a flat flange extending radially a substantial distance outwardly of said U-shaped section and a relatively short inwardly extending flange, said wall section having an end disposed in said ring and having the outer surface thereof lap-sealed to the inner side portion of said U-shaped section to provide a compression seal therebetween, a cup-shaped electrode supporting member extending reentrantly in said wall section and including an outwardly extending flange resting on said inwardly extending flange of said sealing ring, and a discrete flat circular metal member having the inner edge bonded to the outer edge of said flange on said support member and the outer edge registering with and bonded to the outwardly extending flange of said sealing ring, said discrete flat circular member being of substantially more rigid construction than said flanges, whereby it is elfective for minimizing strain transmission to said com pression seal.

8. An electric discharge device comprising a tubular ceramic wall section, a seal ring joined to one end of said wall section, a cup-like electrode reentrant in said one end of said wall section and having a rim portion hermetically joined to said sealing ring through a discrete rigid annular metal element having its outer edge bonded to the outer edge of said sealing ring and its innor edge bonded to said rim portion of said electrode, cooling means positioned in said electrode and including coolant conduit portions extending outwardly of the said cup-like electrode, and a plate-like member positioned over the open end of said cup-like member and having the rim thereof joined to said rigid annular metal element, and said plate-like member having said conduit portions extending therethrough and rigidly joined there- [0.

9. An electric discharge device comprising a tubular ceramic wall section, a sealing ring including an integral U-shaped section, a flat flange extending radially a substantial distance outwardly of said U-shaped section and a relatively short inwardly extending flange, said wall section having an end disposed in said ring and having the outer side surface thereof lap-sealed to the inner side portion of said U-shaped section to provide a compression seal therebetween, a cup-like member extending in said wall section and including an outwardly extending flange resting on said inwardly extending flange on said sealing ring, a discrete flat circular metal member of relatively more rigid construction than said sealing ring having the inner edge bonded to the outer edge of said flange on said cup-like member and the outer edge registering with and bonded to the outwardly extending flange of said sealing ring, cooling means positioned in said cup-like member and including coolant conduit portions extending outwardly thereof, and a discrete second flat circular metal member having the rim thereof bonded to' said first-mentioned circular member, said sealing ring said said second-mentioned flat circular member, said second flat circular member having end portions of said conduit extending therethrough and being rigidly bonded thereto.

References Cited in the file of this patent UNITED STATES PATENTS 1,734,208 Golladay Nov. 5, 1929 2,440,245 Chevigny Apr. 27, 1948 2,569,872 Skehan et al Oct. 2, 1951 2,677,781 Drieschman May 4, 1954 2,782,952 Dalton Febt26, 1957 r 2,789,154 Peterson Apr. 16, 1957 2,890,377 Fyler June 9, 1959 2,939,988 Culbertson et al June 7, 1960 FOREIGN PATENTS 121,879 Russia Aug. 4, 1958 

1. AN ELECTRIC DISCHARGE DEVICE ENVELOPE COMPRISING A TUBULAR CERAMIC WALL SECTION, A METAL SEALING RING INCLUDING AN INTEGRAL GENERALLY U-SHAPED SECTION AND A FLAT FLANGE EXTENDING RADIALLY A SUBSTANTIAL DISTANCE OUTWARDLY OF SAID U-SHAPED SECTION, SAID WALL SECTION BEING DISPOSED IN SAID SEALING RING AND HAVING THE OUTER SIDE SURFACE THEREOF LAP-SEALED TO THE INNER SIDE PORTION OF SAID USHAPED SECTION BY A METALLIC BOND TO PROVIDE A HERMETIC COMPRESSION SEAL THEREBETWEEN, ANOTHER WALL SECTION OF SAID ENVELOPE BEARING ON SAID FIRST-MENTIONED WALL SECTION AND INCLUDING A FLAT RADIALLY OUTWARDLY EXTENDING METAL FLANGE HAVING AN EDGE REGISTERING WITH THAT OF SAID FIRST-MENTIONED FLANGE, AND A METALLIC BOND JOINING ONLY THE REGISTERING EDGES OF SAID FLANGES. 